Penguins are flightless pelagic birds, specially adapted for swimming, porpoising and diving. They are also agile on land, where they come ashore to breed and moult. The wellbeing and successful management of penguins is strongly related to environmental conditions. Penguins breed in very dense colonies in a few restricted areas, providing potentially ideal conditions for the exchange of pathogens - bacteria or viruses capable of causing disease.

King penguins (Aptenodytes patagonicus) frequently strand along the South African coastline. These birds cannot be rehabilitated due to the vast distance to their breeding colonies. They are therefore kept in captive environments such as rehabilitation centres, zoos and aquariums, where they are vulnerable to disease.

In order to develop a disease prevention strategy for its King penguin collection, the National Zoological Gardens of South Africa (NZG) introduced stringent precautionary measures a few years ago. To protect the King penguins from avian malaria, their insect-proof night room was fitted with mosquito-proof netting, fans to ensure constant air flow and a 'bug zapper'. In the evenings the birds are also brought inside before mosquitoes emerge.

The air inside their enclosure is ventilated to protect them from aspergillosis. Fans, sprinklers and misters were placed in and around the enclosure and indoor holding area to rule out heat stress.

In addition, the NZG set out to determine the most common causes of death in its King penguins. Necropsy results attained from the NZG's Animal Record Keeping System (ARKS) from 12 King penguins that died between 1992 and 2009 were examined to determine the cause of death. As the penguins were donated, confiscated from trawlers or washed ashore, the age of the birds was not certain, however all were adults at the time of death.

Of the 12 birds, three died of avian malaria, three of aspergillosis, two of heat stress, one of babesia, one of pododermatitis, one of renal failure, and one of myocarditis.

Mortalities due to malaria occurred in the wet summer months due to the presence of mosquitoes. Similarly, mortalities caused by aspergillosis occurred in the summer months possibly due to high humidity creating a conducive environment for fungal growth.

King penguins are especially susceptible to avian malaria as they evolved in the sub-Antarctic where no mosquitoes are found. The birds have therefore not developed any resistance to the parasite.

The most common diseases causing mortality among NZG King penguins have been identified as aspergillosis, avian malaria and heat stress. NZG research findings are similar to the results obtained for all penguin species as indicated by researchers Fowler & Miller in 2003.

New penguin enclosure

Based on the results of the study, the NZG introduced additional precautionary measures to limit disease. The new King penguin enclosure is completely indoors. Its climate is controlled at 9 to 12°C, artificial marine water will be used, air and water will be filtered, humidity will be closely monitored, it will have a separate hospital room, and pebble tiles and beach sand areas will be included as substrate.

As part of a preventative medicine programme, regular veterinary checks will be conducted on the NZG's penguin collection.

The authors would like to thank Prof Antoinette Kotze, Dr Emily Lane and Dr Ian Espie of the NZG for their valuable assistance throughout the research programme.